PROJECT SUMMARY/ABSTRACT CANDIDATE. Dr. Webb has drawn on her academic achievement and diverse training and experience in clinical and basic science to develop an independent research program. She has developed laboratory skills in molecular and cellular biology and has acquired computational skills in bioinformatics and systems biology. Additionally, her clinical training in Medical Genetics provides her with a strong background in inherited metabolic diseases. Recognition of Dr. Webb's potential as an investigator is reflected in her current appointment of Assistant Professor (tenure-track position, Investigator Track) in the Departments of Genetics and Genomic Sciences (primary) and Pediatrics (secondary) at the Icahn School of Medicine at Mount Sinai. She has been allocated >75% protected research time. Dr. Webb's accomplishments include several first- author publications and additional co-authored manuscripts in high quality journals. CAREER DEVELOPMENT. Dr. Webb's overall long-term career goal is to lead a meaningful and sustainable research program that will allow her to remain a well-established and independent investigator in the fields of metabolism, developmental genetics, and systems biology. These goals will be accomplished through the mentorship, collaboration, and didactic mechanisms outlined in this application. INSTITUTIONAL ENVIRONMENT. The Department of Genetics and Genomic Sciences and the Icahn Institute for Genomics and Multiscale Biology at the Icahn School of Medicine at Mount Sinai is the ideal setting for carrying out the work described in this application. Faculty in the Department are experts in the identification, treatment, and study of inborn errors of metabolism. Additionally, members of the Icahn Institute are world-renown in the ability to use systems biology and computational techniques to study disease. RESEARCH PROJECT. Mitochondrial aminoacyl-tRNA synthetases (mt-ARSs) are essential for protein synthesis in mitochondria, and disruption of mt-ARS function represents a new class of mitochondrial disease. A novel disorder caused by recessive, single nucleotide variants in methionyl-tRNA synthetase 2 (MARS2) associated with developmental delay, growth failure, and sensorineural hearing loss has been identified by the candidate. The proposed project will utilize an integrative approach, combining both wet-laboratory and in silico techniques, to further study mt-ARS disorders. Pathogenic variants in MARS2 will be further characterized biochemically by assessing aminoacylation activity, mitochondrial protein synthesis, and mitochondrial oxygen consumption. To better understand the variable phenotypes and tissue specificity of different mt-ARS disorders, an in vitro model system of several mt-ARS disorders will be developed using CRISPR/Cas9 technologies. RNA-seq data will be generated and network analysis will be completed to identify key drivers and developmental pathways involved in mt-ARS disorders.